Introductory Astronomy textbook

[jdlawlis]

I teach a semester-long Astronomy elective for juniors and seniors at an independent college preparatory high school. For the past few years, I have used Chaisson and McMillan's Astronomy: A Beginner's Guide to the Universe, which has served my purposes well. The course will be changing so that the class will contain 9th graders through 12th graders, and I wonder whether the textbook might not be a little challenging for some students. Does anyone have suggestions for other textbooks that would fit the bill, particularly those that are graphics heavy?

Thanks,
Jeff